Cushioning device for hammer tools



April 1958 G. l. EKSTRCM ET AL 2,831,463

CUSHIONING DEVICE FOR HAMMER TOOLS 2 Sheets-Sheet l Fiied July 7, 1955 Fig.2

#NAAAA? ATTORNEY April 22, 1958 Filed July 7, 1955 Fig. 3

Fig. 4

2 Sheets- Sheet 2 3 IN! M United States Patent CUSHIONING DEVICE FOR HAMlVIER TOOLS Giista Ivar Ekstriim and Sven Vilhelm Sjiigren, Nacka, Sweden, assignors to Atlas Copco Aktiebolag, Nacka, Sweden, a corporation of Sweden ApplicationJuly 7, 1955, Serial No. 520,588

4 Claims. (Cl. 121-36) This invention relates to percussion tools, and more particularly to a cushioning device for handles of such tools by means of which the tools may be held and guided during the work with less fatigue and discomfort to the operator than conventional hand held percussion tools.

One object of the invention is to reduce the shocks transmitted to the operator due to the recoil of the casing of such tools when the hammer piston of the tool is operated. A further object of the invention is to provide a cushioning device which is simple and cheap in manufacture and in which the parts exposed to wear or destruction during operation are cheap and easily interchangeable. A still further object of the invention is to provide a device in which a rubber type cushion of great volume may be used without increasing the overall dimensions of the tool. A still further object of the invention is to provide a device in which a handle for the tool during cushioning movements may be guided on the side bolts of the tool.

For these and other purposes we provide a cushioning device for hammer tools comprising the combination of a casing forming a working cylinder, a fluid actuated reciprocatory hammer piston in said working cylinder, a handle movable axially of said cylinder relative to said casing, means for guiding said handle in said axial movement, means for preventing said handle from turning on the cylinder axis relative to said casing, and annularly disposed cushioning means forming a connection between the handle and the casing permitting cushioned movement of the handle towards the casing in axial direction.

In the accompanying drawings three embodiments of the handle portion of percussion tools provided with a cushioning device according to the invention are illustrated by way of example. Fig. 1 is a partial side elevation and axial section of the rear end of a rock drill of the hammer piston type provided with a cushioning device according to the invention. Fig. 2 is an end view and partial section looking in the direction of the arrows H-H in Fig. 1. Fig. 3 is a side view and partial section of a hammer tool having a closed gun type handle, and Fig. 4 is a similar view of a tool having an open gun type handle.

In the various figures equivalent parts are indicated by the same reference numerals and such parts are only described in connection with Figs. 1 and 2.

In Figs. 1 and 2 a portion of a casing 1 of a hammer rock drill forming a working cylinder 2 is illustrated. The rear end of the casing is covered in conventional manner by a back head 3 and a hammer piston 4 is reciprocable in the cylinder 2 under the action of the working fluid, for instance compressed air, in conventional manner. 5 indicates a bushing provided centrally in the back head 3 and 6 a pipe for supplying flushing water through the tool to the drill steel. The casing 1 and the back head 3 and a not illustrated front head of conventional design are held together by two side bolts 7. Each side bolt 7 has a head 8 for holding the back head 3 against the casing 1. Furthermore, each side bolt has a rear extension 9 for guiding the axial movement of the.

handle and finally a rear end head 10. The bolt heads 8 and 10 form shoulders or abutments between which the.

handle is movable. The handle which serves to guide the tool is generally designated by 11, said handle being provided with rubber sleeves 12 to fitthe hands of the operator and preferably made of soft rubber to form a.

suitable grip and which helps to reduce vibrations corning from the tool and transmitted towards the hands of lar body 13 of resilient material such as soft rubber vulcanised to two tubular steel or metal rings 14 and 15. I

The head 10 engages the ring-shaped portion of the handle as well. as the ring 14 and presses the cushioning device with the ring 15 against a shoulder 16 formed by the.

bushing 5. The extensions 9 of the bolts 7 are fitted in recesses 17 in the handle 11 and the handle rests on an annular shoulder 18 formed by an external flange 25 on the outer ring 14. A recess 26 in the flange 25 permits the flange to move past the head 8 of the bolt.

It is obvious that when in operation a recoil of the casing 1 and the back head 3 causes the ring 15 to move upwardly as shown in Fig. l and the rubber body 13 to be distorted, a very little portion of the recoil will reach the operators hands through the handle portions 12. A rock drill, for instance, provided with the invention is therefore very easy on the operator. The cushioning ring 13, 14, 15 may easily be interchanged when it has been worn out and the only thing to do to replace the cushion device is to disassemble the side bolts 7, 7. The body 13 has approximately the same external diameter as the cylinder diameter and may therefore be given a considable volume, the cross section being substantially square.

In assembling the tool the bolts 7 are first inserted in the recesses 17 of the central portion of the handle 11. The cushioning device 13, 14, 15 is then slid past flattened portions 27 of the heads 8 and fitted between the bolts with the shoulder 18 of the flange 25 against the lower face of the central handle portion, whereupon the bolts are inserted in the back head 3 and the casing 1 and the not illustrated front head of the drill and tightened. The flattened portions 27 serve to prevent the bolts 7 from turning as soon as the ring 14 is in position.

The embodiment illustrated in Fig. 3 differs from the tool in Figs. 1 and 2 only in that the inner ring 15 of the cushioning device 13, 14, 15 rests directly on a shoulder 20 formed on the back head 3 and that the handle 21 is bent to form a closed gun handle.

In the embodiment of Fig. 4 the handle 22 is formed as an open gun handle, whereas the other parts are carried out in the same way as in Fig. 3.

The cushioning devices above described and illustrated in the drawings should be considered only as examples and various modifications may be made of the invention within the scope of the claims. Instead of being fitted on the side bolts of a tool, the handle and cushioning device may naturally be fitted on separate bolts or other suitable means.

What we claim is:

1. In a cushioning device for hammer tools the combination of a casing forming a working cylinder, a back head, a pressure fluid actuated reciprocatory hammer piston in said working cylinder, a handle movable axially of the cylinder relative to said casing, bolts extending axially of the cylinder and arranged for guiding said handle in said axial movement and for preventing said handle from turning on the cylinder axis relative to said casing, two spaced shoulders on each bolt one forming a means for limiting rearward motion of the handle on the bolts and the other forming a means for holding said back head to said casing, a ring shaped cushioning body of relatively soft yieldable material and inner and outer stiff tubular rings between which and to which said ringshaped body is secured, said handle resting on said outer ring and said inner ring resting on said back head to provide a cushioning connection between the back head and the handle.

2. A cushioning device according to claim 1 in which said outer ring is provided with an external annular flange forming a shoulder for the handle for taking up forward pressure on the handle.

7 3. A cuhioning device according to claim 1 in which spaced shoulders on said bolts are formed by spaced heads provided on the bolts.

4. A cushioning device according to claim 1 in which said outer ring is provided with an external annular flange forming a shoulder for the handle for taking up forward pressure on the handle, and in which said spaced shoulders on said bolts are formed by spaced heads provided on the bolts, and in which a recess is provided in said flange to permit the ring and flange to move axially without interfering with the forward heads on the bolts, said forward heads being formed with flattened surfaces to cooperate with the ring for locking the bolts against turning in the handle.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Vibration Control, catalogue, Lord Mfg. Co., 1941, pages 13 and 16. 

